In the field of wire production, the manufacturing process based on drawing has widespread use. The drawing tools used in this process generally have a wear-resistant inner mandrel and a holding body which encloses and secures the mandrel against displacement. In the middle of the mandrel, a profile drawing die is placed for the purpose of adjusting wire diameter to the exact value desired.
In a conventional wire production manufacturing process, a significant number of drawing tools employ a profile die formed in the mandrel which allows drawing the raw wire from one direction only. In conjunction with this single direction drawing tool die, the holder enclosing the mandrel may in practice also be loaded from one direction only. Drawing tools of this type are described in U.S. Pat. Nos. 4,144,739; 4,365,502 and 4,392,397.
For the single direction drawing tool arrangements set forth in the above 3 U.S. patents, there is an inherent disadvantage in that, once the die has been worn down due to high loading thereby resulting in a worn and fissured surface on the profile drawing die, such die can only be salvaged by repair to a limited extent. In other words, such die may be cut down (e.g. expanded in size) to remove the uneven, worn or fissured surfaces, but only to the extent that the resultant smooth surface of the die, has a dimension that allows the drawing of the raw wire therethrough so as to maintain the finished product at a dimension within the upper tolerance limit of the wire cross-section. Of course, when the upper tolerance limit is exceeded, the tool can no longer be used for drawing the given wire. It can be a appreciated that in high speed manufacturing operations, the need to stop the automated system in order to do a tool changeover is inefficient both in terms of time and cost and therefore should be minimized. In order to alleviate this problem and to increase tool lifetime, "double-profile" drawing tools were developed wherein the mandrel has a profile drawing die suitable for bi-directional use. A drawing tool of this type is described in U.S. Pat. No. 4,462,242. Though providing the advantage of extended life over the drawing tool having a single direction operation, the double-profile drawing tool of this patent has the disadvantage of providing a less secure mounting arrangement of the mandrel within the housing body. As such, in the case of when a hot drawing process is used, the temperature rise due to high loading on the mandrel can cause the mandrel to loosen thereby resulting in a failure of the drawing tool. To explain this, it should be understood that the means for securely mounting the mandrel within the housing body so as to prevent displacement or the exercise of undue stresses to the tool during high speed operation, must allow for the ability to load the tool to its maximum capacity even if such capacity causes a temperature rise. If the holder body enclosing the mandrel is a band that does not fit appropriately to the mandrel so as to securely encircle the mandrel or perhaps reduce or take-up some of the load forces to which the mandrel is exposed, the mandrel can crack and become unstable. Additionally, if the mandrel is not secured against movement, the profile die can come out of alignment thereby resulting in a change of the optimum forming profile in using the drawing tool.